1. Field of the Invention
The present invention relates to an improved cutting head for line trimmers used to cut vegetation; in particular, the present invention is an improved cutting assembly adapted for use in either spooled or fixed length filament line trimmers.
2. Description of Related Art
Commercially available line trimmers employ one of two methods to achieve their goal of vegetation cutting. Some line trimmers have a spooled filament, wherein the filament is supplied by a spool located in the interior of the line trimmer housing. Other line trimmers have a fixed length filament that is anchored at a point in the interior of the line trimmer cutting head.
In line trimmers that have a spooled filament, fresh filament is supplied by a spool either automatically or manually. Fresh filament is needed when the filament being used is accidentally cut or becomes worn out from repeated use. However, restoring the length of cutting filament can be a tedious process because tangling of the cutting filament commonly occurs. Furthermore, when a spool of filament has been exhausted, the spool must be replaced with a new spool of filament.
Fixed line trimmers have cutting heads that contain cutting filaments of a discrete length. The fixed length filament is attached to an inner portion of the cutting head, such that the free end of the filament will be extended into proper cutting position by centrifugal force caused by rotation of the cutting head. Some fixed line trimmers require that a portion of the cutting head be disassembled in order to install a new cutting filament when the previous filament becomes worn or shortened through repeated use. Fixed line trimmers that do not require disassembly of the cutting head to install a new filament often require that the cutting filament have a specific shape, or require careful manipulation of the cutting filament in order to secure the filament to the cutting head. The cutting assembly of the present invention addresses these, as well as other problems often associated with line trimmers found in the prior art, as exemplified as follows.
U.S. Pat. No. 4,054,993 issued on Oct. 25, 1977 to Walter B. Kamp et al. describes a rotary cutting assembly for cutting vegetation with a spooled, flexible, whirling flail. The cutting assembly comprises an elongated linear shaft extending along a rotatable vertical axis, a horizontal base-plate in co-rotatable association with the lower part of the shaft, retainer means attached to the base-plate, and an elongated horizontal flexible flail that extends radially outwardly from the retainer means along a horizontal axis. The flail is constructed from a resinous material and consists of a central core and an external contoured surface of varying cross-sectional sizes formed by prominent protuberances surrounding the central core.
U.S. Pat. No. 4,145,809 issued on Mar. 27, 1979 to Raymond E. Proulx describes a cutting head for rotary mowers, trimmers, and edgers having a rotating body from which spooled, flexible, flail-like filamentous cutting blades extend radially therefrom. The flail-like cutting blades are made of a polymer such as nylon monofilament. The flail-like cutting blades exit from the rotating body through grommets. The cutting head has raised ramp portions alongside each grommet to protect the grommet. The top of the rotating body has sharp-edged radial ribs that operate to deter weed and grass stems from wrapping and binding about the upper portion of the rotating body.
U.S. Pat. No. 4,223,441 issued on Sep. 23, 1980 to Robert G. Everts describes a rotary vegetation cutter comprising a spooled flail attached to a rotor. The flail comprises a plurality of metal filaments braided into an elongated strand, wherein an abradable jacket surrounds the strand. The jacket is made of an abradable material so it can wear off at the tip and expose the metal filaments.
U.S. Pat. No. 4,571,831 issued on Feb. 25, 1986 to Donald M. White, III describes a fixed length of non-metallic filament mounted to a cutting head capable of rapid rotation. The cutting head contains a filament retainer cup that has two diametrically opposed V-shaped slits used to secure the fixed length filament. The cutting head also contains abutments that prevent vibrations caused by the filament contacting vegetation from migrating inwardly to the retention points of the V-shaped slits which causes an excessive build-up of heat that would damage the filament.
U.S. Pat. No. 4,756,146 issued on Jul. 12, 1988 to Russell V. Rouse describes a fixed plastic cutting line trimmer head for cutting vegetation. The trimmer head consists of a pair of overlying sheet steel circular plates welded together to form two or more pairs of partially circular passages between the plates opening at each end into a recess extending continuously at and between the periphery of the plates. The passages are formed by recesses formed in the plates in registry with each other while the peripheral recess is formed by outwardly flared portions of the plates. A fixed length of cutting line is placed into both passages by inserting the end of the line into the adjacent ends of the passages, and sliding the opposite end portions through the passages until they emerge from the remote ends of the passages, with an intermediate portion of the line engaged against a land located between the adjacent passage ends.
U.S. Pat. No. 5,615,543 issued on Apr. 1, 1997 to Hyram J. Caffey et al. describes a rotary cutting head adapted for attachment to conventional line trimmers. The rotary cutting head consists of a cutting disk having a circular plate and a peripheral side wall integral with the circular plate. The peripheral side wall has a pair of integral gussets, each having a pair of radial bores that pass through the side wall. A flexible cutting filament of a thermoplastic material is frictionally engaged within each pair of radial bores such that one end of the cutting filament extends outwardly from the peripheral side wall. The cutting filament consists of a flexible shaft portion that has an integral retaining flange at one of its ends. The retaining flange is formed by contacting one end of the filament with a sufficiently heated surface to permit localized melting of the thermoplastic material at the point of contact with the heated surface. The retaining flange secures the cutting filament to the cutting head.
U.S. Pat. No. 5,671,536 issued on Sep. 30, 1997 to Robert G. Everts et al. describes a spooled line trimmer head having a line feed configuration that facilitates automatic reloading of the trimmer head with new line without requiring removal of the spool from the housing. The line is received into the housing through an eyelet on the housing and is secured in a hole formed on a flange of the spool. The line is wound around the spool while the spool remains inside the housing.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the present invention. The aforementioned prior art does not describe a cutting assembly lacking a point of attachment directly within the cutting head hub, wherein the cutting assembly is attached to the hub through apertures in the housing wall of the cutting head hub, thereby enabling the cutting assembly and cutting head hub to rotate as a single unit. Therefore, there exists a need for a cutting assembled that is easily installed and readily adaptable to accommodate either spooled or fixed length filament containing conventional line trimmers. The vegetation cutting capabilities of commercially available line trimmers can be substantially improved by substituting their original cutting means with the cutting assembly of the present invention.